What is the maternity 21 blood test? How sensitive and specific is it? Does it have false positive rate?

False positive. Prenatal testing for chromosomal abnormalities can help determine whether your baby has certain genetic conditions. Knowing more about the health of your baby can help you, your family and your health care provider make informed decisions about your pregnancy. For a more detailed clarification i would suggest a consultation with your ob/gyn to get more information.